A Reply to the Attacks on Climate Change Science

The Union of Concerned Scientists today issues a response to some of the recent criticisms about the Intergovernmental Panel on Climate Change. (We also recently posted a set of pro and con columns on the expansion of nuclear power in conjunction with the UPC.) Rather than paraphrase the report, we've posted it in full below. Please add your comments below and if you'd like to reply in a more full manner, please contact us.

Over the last few months, the Intergovernmental Panel on Climate Change (IPCC) has been attacked for minor errors in its sprawling 2007 report on climate change. To set the record straight and provide appropriate scientific context, the Union of Concerned Scientists has assembled a series of explanatory backgrounders on specific allegations about the report.

Overall, the IPCC's conclusions remain indisputable: Climate change is happening now and human activity is causing it. Nations around the world will have to adapt to at least some climate change, including sea level rise, changes in precipitation, disruptions to agriculture, and species extinctions. But if we dramatically reduce our emissions, we can prevent the worst effects of climate change.

The IPCC is the world's leading body for assessing climate science. It was established in 1988 by the World Meteorological Organization (WMO) and the U.N. Environment Programme (UNEP) in recognition of the problem of global warming. Through the IPCC, climate experts from around the world synthesize the most recent climate science findings every five to seven years and present their report to the world's political leaders. Thus far, the IPCC has issued comprehensive assessments in 1990, 1995, 2001 and 2007.

The IPCC's 2007 report is the most comprehensive synthesis of climate change science to date. Experts from more than 130 countries working over six years contributed to the assessment. More than 450 lead authors received input from more than 800 contributing authors, and an additional 2,500 experts reviewed the draft documents.

The 2007 report is comprised of three sections, or working groups, that focus on the scientific basis of global warming (Working Group I), its consequences (Working Group II), and options for mitigation (Working Group III). The IPCC released summaries of the three working group documents over the course of 2007, culminating in the publication of the final "synthesis report" at the end of the year.

The inclusive and transparent process by which IPCC assessments are developed, reviewed and accepted by experts and governments helps ensure scientific credibility and value for informing officials when they formulate climate policies. As with any human endeavor, errors are possible. It is a testament to the quality of the IPCC that errors have been few, and when identified, they have been corrected. A concerted effort to improve the quality of the IPCC process is essential.

The second of three 2007 IPCC reports included a statement that the likelihood that Himalayan glaciers will disappear "by the year 2035 and perhaps sooner is very high." It is not clear how this unsupported assertion made it into the report, although it was openly challenged by some researchers during the review and editing process. On January 20, the IPCC released a statement (pdf) on this issue. It says, in part, "The Chair, Vice-Chairs, and Co-chairs of the IPCC regret the poor application of well-established IPCC procedures in this instance."

The claim was part of the full review of climate science and impacts provided in the dense, 3,000-page report, but was not mentioned in its highly visible summaries for policymakers. Presumably the working group did not consider the 2035 Himalayan glaciers claim to be reliable enough for its policymaker summary. The statement in the summary was much less specific. "If current warming rates are maintained," it stated, "Himalayan glaciers could decay at very rapid rates."

Given the sprawling nature of the IPCC, it is not surprising to find relatively minor errors. Such mistakes do not undermine the overall conclusions of the organization's reports, which are subject to an exhaustive review process.

What should not get lost is the fact that glaciers around the world are melting rapidly.

A 2005 global survey of 442 glaciers from the World Glacier Monitoring Service found that only 26 were advancing, 18 were stationary, and 398 were retreating. Overall, about 90 percent of the world's glaciers that scientists have measured are shrinking as the planet warms.

Because scientific understanding of how fast snow and ice is responding to global warming is still developing, the IPCC largely left the effect of melting glaciers and ice sheets out of its sea-level rise projections in 2007 and primarily considered the effects that thermal expansion has on the ocean.

New analyses indicate that the shrinking land-based ice could lead to a sea-level rise of 2.6 feet (0.8 meter) by the end of the century; and, although 6.6 feet (2.0 meters) is less likely, it is still physically possible.

Melting glaciers and the resulting sea-level rise are a threat to coastal communities around the world. According to the U.S. Global Change Research Program's 2009 review of climate impacts in the United States, "Sea-level rise and storm surge place many U.S. coastal areas at increasing risk of erosion and flooding, especially along the Atlantic and Gulf Coasts, Pacific Islands, and parts of Alaska. Energy and transportation infrastructure and other property in coastal areas are very likely to be adversely affected."

Melting glaciers also will threaten drinking water supplies. An August 2008 Geophysical Research Letters study that examined the impact of the melting Himalayan Naimona'nyi glacier concluded, "If Naimona'nyi is characteristic of other glaciers in the region, alpine glacier meltwater surpluses are likely to shrink much faster than currently predicted with substantial consequences for approximately half a billion people."

A sentence in Chapter 13 of the 2007 IPCC Fourth Assessment Report on Impacts, Adaptation and Vulnerability states: "Up to 40 percent of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation."

In other words, climate change makes drought in the Amazon basin more likely. In drought years, trees are more likely to die and forests become more susceptible to fires. In wet years, fires often stop at the forests' edge because the forest soil is so moist.

It would have been preferable for the IPCC to have cited the original scientific peer-reviewed literature rather than the WWF-IUCN report. Further, the WWF-IUCN report was scientifically correct, but it did not cite the correct papers by Dan Nepstad, a senior scientist at the Woods Hole Research Center on Cape Cod, and his colleagues.

"The WWF correctly states that 630,000 km2 of forests were severely drought stressed in 1998 -- this figure comes from Nepstad et al. 1999. However, the 40 percent figure comes from several other papers by the same author that the WWF failed to cite. A 1994 paper estimated that around half of the Amazonian forests lost large portions of their available soil moisture during drought (Nepstad et al. 1994). In 2004, new rainfall data showed that half of the forest area of the Amazon Basin had either fallen below, or was very close to, the critical level of soil moisture below which trees begin to die (Nepstad et al. 2004). The results from these papers are consistent with the original statement: 'Up to 40 percent of the Brazilian forest is extremely sensitive to small reductions in the amount of rainfall.'"

It is also worth nothing that Nepstad and other researchers further confirmed the link between drought and fire in papers published after the IPCC's deadline for research that could be included in this section of its 2007 report.

Cook continues:

"Subsequent research has provided additional confirmation of the Amazonian forest's vulnerability to drought. Field measurements of the soil moisture critical threshold found that tree mortality rates increase dramatically during drought (Nepstad et al. 2007). Another study measured the effect of the intense 2005 drought on Amazonian biomass (Phillips et al. 2009). The drought caused massive tree mortality leading to a fall in biomass. This turned the region from a large carbon sink to a carbon producer. The paper concluded that 'such events appear capable of strongly altering the regional carbon balance and thereby accelerating climate change.'"

While the IPCC should have cited the original peer-reviewed literature, not a summary of that literature by WWF and IUCN, the basic science was sound. And regardless of how the IPCC cited the references, tropical forests are increasingly vulnerable to drought and fire because of climate change as well as from forest degradation from destructive logging practices.

There is a clear scientific consensus -- based on the conclusions of many peer-reviewed papers -- that climate change is causing an increase in storms with heavy precipitation. This is due in part because warmer air retains more moisture, setting the stage for heavier rain and snow storms in areas that typically experience rain or snow. Between 1958 and 2007, New England saw a 67 percent increase in heavy precipitation events and the Midwest experienced a 31 percent increase, according to the 2009 federal report "Global Climate Change Impacts in the United States." The report documented a 20 percent average increase for the entire country.

The 2007 IPCC report also was clear about how climate change would affect hurricanes. It concluded that hurricane intensity worldwide likely would increase, and that there could be fewer weak hurricanes. The report included numerous references to peer-reviewed studies that draw this conclusion, which was confirmed by studies conducted by the National Oceanic and Atmospheric Administration and other institutions.

The science linking climate change to increased severity of extreme weather is well-substantiated in peer-reviewed literature. Even so, some contrarians have recently cited another, older controversy to try to give the false impression that these findings are in question. That controversy centers on how the 2007 report characterized the economic cost of an increase in severe weather. Contrarians specifically point to a complaint by Roger Pielke Jr., a University of Colorado environmental studies professor, that the 2007 report misrepresented the reasons why economic losses from natural disasters have significantly increased over the years. Pielke says that the primary drivers for increased costs are economic factors, such as changes in wealth and population along the coasts.

The IPCC report did not dispute that fact, and it prominently cited Pielke's research. It also cited one study that suggested that factors other than economic ones may be driving costs, but included a number of caveats in that citation. This is in keeping with the IPCC's task of presenting a balanced view of the literature. Specifically, the report concluded in its "Summary for Policy Makers" section: "Costs and benefits of climate change for industry, settlement [cities and towns] and society will vary widely by location and scale. In the aggregate, however, net effects will tend to be more negative the larger the change in climate." And it found: "Where extreme weather events become more intense and/or more frequent, the economic and social costs of those events will increase, and these increases will be substantial in the areas most directly affected."

Pielke specifically objected to the IPCC including unpublished material on economic costs of natural disasters in its 2007 report. This practice, however, is not unusual for the IPCC. IPCC procedures state that "…it is increasingly apparent that materials relevant to IPCC reports, in particular, information about the experience and practice of the private sector in mitigation and adaptation activities, are found in sources that have not been published or peer-reviewed (e.g., industry journals, internal organizational publications, non-peer reviewed reports or working papers of research institutions, proceedings of workshops, etc)." The IPCC provides guidelines for the inclusion of such research, including clear citation. In any case, more published research is needed on the economic costs of climate change.

Climate contrarians are falsely claiming Eastern Chinese temperature data first published in a 1990 Nature paper is compromised by the "urban heat island" effect. The term refers to the fact that buildings and asphalt are darker than surrounding countryside, often making cities and population centers hotter. Scientists have studied this effect since the mid-1800s and it is extensively referenced in the scientific literature. Overall, climate science indicates that the urban heat island effects has no bearing on global temperature trends and is insignificant compared to other adjustments routinely made to make temperate records more accurate,

When scientists measure global warming, they examine how much temperatures have changed over time. For instance, an urban station may have warmer thermometer readings compared with a rural station in the region, but global warming will cause temperatures to rise at both stations. To determine trends, scientists compare the difference between the temperatures at stations today and their average temperatures in the past.

Scientists worldwide, including those at leading American institutions, routinely correct station data for changes such as shifts in station location, different elevation, different time of daily observation, different latitudes, and instrument changes over time. For example, after such adjustments for stations across the United States, there was no detectable difference between urban and rural stations comparisons in each region.

Climate contrarians are using the Eastern Chinese temperature data to try to link manufactured controversies over citations in the IPCC's 2007 report and the content of stolen emails from the University of East Anglia's (UEA) Climatic Research Unit that were published online late last November. UEA has issued a statement rebutting these claims and addressing some freedom of information concerns raised by a recent story in the Guardian, a British newspaper. According to UCS, UEA could do more to be transparent, particularly by making relevant documents related to these and other charges easily accessible online.

The 2007 IPCC report does cite papers on the Eastern Chinese data -- along with thousands of other papers. And some of the stolen emails included passages that mentioned the Chinese data. But just like the previous manufactured controversies, these accusations shed little light on the science in question.

In fact, the Eastern China temperature data referenced in the Guardian article and other news stories are reliable and are only a minuscule part of the global temperature record data that indicate that the Earth's average temperatures are rising. It should be noted the "urban heat island" effect does not in any way affect the vast number of temperature records measured outside of cities or in the ocean.

Eastern China is warming in a way consistent with the rise in global average temperatures. The 1990 Nature paper in question was backed up by several other studies, as the University of East Anglia noted.

When University of East Anglia Climatic Research Unit Director Phil Jones and other researchers conducted their 1990 research, they found little difference in temperature between 42 urban stations and 42 suburban temperature stations in Eastern China. A 2008 study by Jones and other researchers, which examined 728 temperatures stations in Eastern China, confirmed that there was an insignificant difference between temperatures in urban and suburban areas. However, by comparing the difference between all the Eastern China land stations to the nearby ocean temperatures, the 2008 paper did find significant warming from increased urbanization on the land -- 0.1 degrees Celsius per decade between 1951 and 2004. Overall, the study found Eastern China warmed 0.8 degrees Celsius over the same time period largely due to global warming.Chinese temperature records are reliable and consistent with global warming